What is a cataract?
To understand how cataracts form we first need to understand what a cataract is. A cataract happens when the natural crystalline lens in the eye becomes cloudy and opaque. Everybody is born with a lens in their eye, and unless congenital cataracts are present, it is clear. The lens is inside the eye, right behind the iris (the colored part of your eye). This is why an eye doctor must dilate your eyes to evaluate for the presence of a cataract. The lens is made up of proteins, and increases in size over a lifetime by adding layers (kind of like a tree). When these proteins are precisely aligned with each other they result in a clear lens.
provides an “optical cross-section” through the clear lens in a 13-year-old eye.
With the help of our cornea, the lens focuses light onto our retina to form a clear image. When a cataract starts to form, the proteins in the lens can clump together and lose their clarity. This results in the symptoms of a cataract, most commonly blurred vision and glare from point sources of light. Contrast sensitivity (ability to see in low or dim light) and color perception is also commonly affected. One of the most common things I hear after performing cataract surgery on a patient’s first eye is they can’t believe how much more vibrant colors are! They often exclaim that they didn’t really know what white looked like, and that everything looks yellow out of the other eye that still has a cataract!
Why do cataracts happen?
The scientific answer is because of changes to the protein structure inside the lens that causes a loss of clarity. When people ask this question they usually are asking about risk factors for cataract development. The biggest risk factor for cataract development is age. I sometimes jokingly tell people that if they live long enough they will develop cataracts….although I recently did cataract surgery on a healthy 96-year-old and his cataracts were of only average cloudiness. So while everyone develops cataracts as they age they develop them at varying rates. Other risk factors for cataract formation include diabetes and smoking. Steroid use can also cause cataract formation in young people. A year or two ago I did successful cataract surgery on a young woman who developed cataracts after taking oral steroids for rheumatoid arthritis. There are other less common systemic diseases that can also contribute to cataract formation. Currently, cataract surgery is the only way to treat cataracts.
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